Field Measurements of Ammonia Volatilization from Surface Applications of Ammonium Salts to a Calcareous Soil1

W. L. Hargrove,

D. E. Kissel and

L. B. Fenn2

Abstract

Abstract

Many laboratory experiments have been conducted to study ammonia volatilization from N fertilizers, but few experiments have been conducted under field conditions. The objective of this study was to evaluate ammonia volatilization in the field from ammonium sulfate and ammonium nitrate applied to the surface of a calcareous soil, Houston Black Clay, that belongs to the fine, montmorillonitic, thermic family of Udic Pellusterts. Volatilization was evaluated indirectly by measuring N uptake by Coastal bermudagrass (Cynodon dactylon L.) and directly by measuring ammonia as it volatilized. In the field plot study, estimated losses ranged from 3 to 10% of the applied N for ammonium nitrate, from 36 to 45% of the applied N for pelleted ammonium sulfate, and from 25 to 55% of the applied N for liquid ammonium sulfate at rates of 140 and 280 kg N/ha. Direct measurements of ammonia losses from pelleted ammonium sulfate were 47, 43, 59, and 50% of the applied N in late summer, 1975, and 39, 30, 27, and 35% of the applied N in spring, 1976, at rates of 33, 66, 140, and 280 kg N/ ha. The lower loss of ammonia in the spring was apparently in response to lower soil temperatures at that time. Consistent diurnal fluctuations in ammonia losses occurred at both times. These fluctuations corresponded closely with daily fluctuations in the atmospheric relative humidity. These results agree with earlier laboratory studies in that ammonium sulfate loses considerably more ammonia than ammonium nitrate when applied to the surface of a calcareous clay soil.

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